Heavy equipment manufacturers typically employ hydraulic actuators to move and articulate arms, booms, buckets and auxiliary tools. These auxiliary tools can include hydraulically actuated attachments, such as scoops, fingers and grapples. All are employed with conventional backhoes and excavators. “Thumbs” are another articulating auxiliary tool often used with a bucket. The thumb is typically employed to grasp larger objects, such as tree trunks or boulders.
Examples of such thumbs are found in U.S. Pat. No. 6,640,471 to Desrochers, which shows a thumb and bucket combination. The thumb attaches to a boom arm of an excavator or other earth moving equipment, near a pivoting bucket. The thumb may be added to the arm as a retrofit. However, this requires the permanent attachment of a large mounting bracket to the arm, and the attachment of extension plates to the bucket. The forces involved in the operation of the thumb places significant mechanical stresses on these extension plates. Additionally, the thumb's pivot is separated from the bucket's pivot by a suggested distance of about eight inches. This separation is typical of several prior retrofit thumb pivots, all unable to coincide, or line-up with the bucket pivot. A closer attachment is not feasible.
U.S. Pat. No. 5,111,602 to Risch, and U.S. Pat. No. 5,553,408 to Townsend teach extensive thumb retrofits requiring that the hinge pin of the bucket be lengthened, allowing a direct attachment of the thumb to the extended pin. This direct attachment provides for an improved gripping action by the thumb, without walking or rotating of the grasped object as the thumb and bucket rotate together. However, it is observed that the bucket pin is difficult to remove and replace with the needed precision. With this cumbersome modification of the bucket pivot to accommodate the thumb pivot, these prior thumbs are very difficult to properly install.
Therefore, a retrofit thumb for use with heavy equipment is needed that is easy to attach and detach from an arm or boom, and cooperatively actuates with an existing bucket to eliminate walking of the grasped object.
Additionally, these prior actuated thumb retrofits fail to account for the added stresses incurred to the boom mechanism and bucket. Therefore, a thumb apparatus is needed that can attach to a heavy equipment boom member quickly and economically, without requiring a refitting of the bucket pivot, strengthening or “beefing up” the boom member, or any such major changes to the structure, design or configuration of the boom member, the bucket, or the heavy equipment to which the thumb apparatus is mounted.
The present invention addresses these shortcomings of prior thumbs and will be better understood by reference to the following detailed description taken in conjunction with the accompanying drawings.